Various techniques have been used for welding plastic tubes particularly as used in the medical field. U.S. Pat. No. 7,398,813 describes a device having a first tube holder and a second tube holder. Each of the tube holders has first and second parallel tube holding areas in line with each other. In practice a first tube would be placed in the aligned first tube holding areas across the location where the tube holders are adjacent each other. A second tube would be similarly placed in the aligned second tube holding areas. A tube clamp in each of the first tube holding areas clamps the first tube to create a generally fluid free area of the first tube. A tube clamp is similarly provided in the second tube holding areas to create a generally fluid free area of the second tube. At least one of the clamps is laterally movable while the clamps are maintained in their clamping condition. To increase the length of the fluid free area preferably both clamps of one of the tube holders are laterally movable by having that tube holder moved laterally. Such movement is performed after the tubes are initially loaded in a loading station, then the one tube holder is laterally moved in a stripping station to increase the size of the fluid free area. Thereafter, the tubes are cut. In U.S. Pat. No. 7,398,813 the cutting is done with a non-heated cutting device, such as a cold blade, and the tube holders are then moved to a heating station while the clamps are still maintained in their clamping condition. In the heating station a heating device heats/melts the cut stub ends of the tubes. The cut ends of the tubes are realigned so that a cut stub end of the first tube becomes aligned with a cut stub end of the second tube and these two aligned heated/melted cut stub ends are then shifted into contact with each other to become welded together.
The specific arrangement for clamping the tubes disclosed in U.S. Pat. No. 7,398,813 includes clamp jaws of different construction in one tube holder as compared with the other tube holder. More particularly the compressed tubing is held tight by square jaws in one tube holder while the jaws in the other tube holder are smooth jaws to allow the tubing to slip through the smooth jaws.